A,B为税角求证sinB/sinA=cos(A+B)
求证:cos(a+b)=cosa*cosb-sina*sinb
求证sin(2A+B)/sinA-2cos(A+B)=sinB/sinA
求证sina+sinb=2sin(a+b)/2*cos(a-b)/2
求证: sina+sinb=2sin[(a+b)/2]cos[(a-b)/2] cosa+cosb=2cos[(a+b)
已知A,B为锐角,SinA/SinB=Cos(A+B)求TanA的最大值
在△ABC中,求证:sinA+sinB+sinC=4cos(A/2)cos(B/2)cos(C/2)
11.在△ABC中,求证sinA+sinB+sinC=4cos(A/2)cos(B/2)cos(C/2)
已知cos(a+B)+1=0,求证sin(2a+B)+sinB=0?(提示:sin(-a)=-sina).
已知sina*sinb=1,求cos(a+b)
证明:cos(a+b)=cosa*cosb-sina*sinb
求证sina-sinb=2cos(a+b)/2*sin(a-b)/2这个怎么证明?
已知cos(a-b)=3/1,求(sina+sinb)(sina+sinb)+(cosa+cosb)(cosa+cosb